The Effect of Rotation Velocity in Vertical Centrifugal Casting Process on the Hardness and Physical Characteristics of Al-Si Alloy (Re-melting Used Pistons) with Core and Without Core

Metal casting is a metal forming process that can produce complex shapes. CentrifugalCentrifugal casting is widely used to make cylindrical objects. One of the advantages of centrifugalCentrifugal casting is that it can produce graded properties. This study examines the effect of rotational speed on density, microstructure and hardnessHardness in the vertical centrifugalCentrifugal casting process, and will also compare processes using cores and without cores. This study used re-melting used pistons materials and spectro tests were conducted, where the results showed aluminum alloy materials with the main additional elements Si and Cu. The metal melting process is conducted to a temperature of 750–800 °C, while the mold is preheated with acetylene weldingWelding up to 500 °C. Molten metal is poured into the mold at 750 °C then the mold is rotated for 3 min. CentrifugalCentrifugal casting rotation variations are 400, 600,800 and 1000 RPM. The casting is cylindrical in shape with a diameter of 130 mm and a height of 35 mm. Each variation of casting speed is tested for porosityPorosity, microstructure observation and Brinell hardnessHardness test. The results of the porosityPorosity test showed a gradation of increasing the percentage of porosityPorosity from the outside diameter to the inside diameter. The microstructure formed on the outer diameter is finer and needle-shaped, while the inner diameter tends to be coarser and larger in shape. The results of the properties test obtained the lowest hardnessHardness value at 400 RPM (74.55 BHN) with a porosityPorosity of 1.8%. While the highest hardnessHardness value is at 1000 RPM (76.8 BHN) with a porosityPorosity of 2.24%.